Methods: Using MEDLINE (January 1966 through December 2004) studies involving human subjects that examined the effect of garlic (Allium sativum) on serum lipids and blood pressure were obtained. Studies that were conducted using garlic in the form of garlic powder tablets were included in the data extraction. Correlation coefficients were calculated for total serum cholesterol, systolic and diastolic blood pressure with respect to date of publication. Trials published prior to January 1994 were placed into an “earlier” group and compared to the “latter” group of studies published from January 1994 onward.
Results: Eighteen trials were identified whereupon the inverse associations between total serum cholesterol, systolic and diastolic blood pressures with respect to time of publication were correlated (−0.614, −0.627, and −0.587 respectively, p < 0.05). No significant associations were observed between systolic and diastolic blood pressure with respect to total serum cholesterol (0.388 and 0.431 respectively). The following differences between the earlier and later groups were observed for total serum cholesterol (31.4 ± 19.0 vs. 3.5 ± 5.8 mg/dl, p = .004); systolic blood pressure (11.0 ± 9.2 vs. 2.0 ± 4.4 mmHg, p = .133) and diastolic blood pressure (5.8 ± 3.4 vs. 0.9 ± 2.4 mmHg, p = .018).
Conclusions: Publications published prior to January 1994 performed better than those published after January 1994, suggesting that allicin may be responsible for the antihypertensive effects of garlic powder tablets. However, a lack of correlation between changes in total serum cholesterol and blood pressure suggests that other organosulfur compounds may also play a role in the antihypertensive mechanisms of garlic.
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